Shifting and gear assembly for transmission

Abstract

A shifting and gear assembly for a transmission has: a hollow shaft; first and second gears on the hollow shaft, the hollow shaft defining at least one first aperture and at least one second aperture in axial alignment with the first and second gears respectively; at least one first cam follower and at least one second cam follower disposed in alignment with the at least one first aperture and the at least one second aperture respectively; a cam disposed in the hollow shaft, the cam having a minimum cam contact surface having a width measured in a direction parallel to a central axis of the hollow shaft. A distance between the first and second cam followers is less than or equal to 1.1 times the width of the minimum cam contact surface. A shift actuator is operatively connected to the cam for selectively translating the cam in the hollow shaft.

What is claimed is: 
     
         1 . A bicycle transmission comprising:
 an input shaft;   a first shifting and gear assembly;   a second shifting and gear assembly,   each of the first and second shifting and gear assemblies comprising:
 a hollow shaft parallel to the input shaft; 
 a first gear rotationally mounted on the hollow shaft, the hollow shaft defining at least one first aperture in axial alignment with the first gear; 
 at least one first cam follower disposed in alignment with the at least one first aperture; 
 a second gear rotationally mounted on the hollow shaft, the hollow shaft defining at least one second aperture in axial alignment with the second gear; 
 at least one second cam follower disposed in alignment with the at least one second aperture; 
 a cam disposed in the hollow shaft, the cam having a minimum cam contact surface, the minimum cam contact surface having a width measured in a direction parallel to a central axis of the hollow shaft, a distance measured in the direction parallel to the central axis of the hollow shaft between the at least one first cam follower and the at least one second cam follower being less than or equal to 1.1 times the width of the minimum cam contact surface; and 
 a shift actuator operatively connected to the cam, the shift actuator selectively translating the cam in the hollow shaft along the central axis of the hollow shaft, 
 in response to the cam being axially aligned with the at least one first cam follower, the cam displacing the at least one first cam follower radially outward to engage the first gear to rotationally fix the first gear to the hollow shaft, 
 in response to the cam being axially aligned with the at least one second cam follower, the cam displacing the at least one second cam follower radially outward to engage the second gear to rotationally fix the second gear to the hollow shaft; 
   a third gear mounted to the input shaft, the third gear being rotationally fixed relative to the input shaft, the first gear of the first shifting and gear assembly engaging the third gear;   a fourth gear mounted to the input shaft, the fourth gear being rotationally fixed relative to the input shaft, the second gear of the first shifting and gear assembly engaging the fourth gear;   an output shaft parallel to the hollow shafts of the first and second shifting and gear assemblies, the output shaft being driven by the hollow shafts of the first and second shifting and gear assemblies;   a fifth gear mounted to the output shaft, the fifth gear being rotationally fixed relative to the output shaft, the first gear of the second shifting and gear assembly engaging the fifth gear; and   a sixth gear mounted to the output shaft, the sixth gear being rotationally fixed relative to the output shaft, the second gear of the second shifting and gear assembly engaging the sixth gear,   the hollow shafts of the first and second shifting and gear assemblies being integrally formed as a single countershaft.   
     
     
         2 . The transmission of  claim 1 , wherein, for each of the first and second shifting and gear assemblies, the shift actuator is an electric shift motor. 
     
     
         3 . The transmission of  claim 1 , wherein, for each of the first and second shifting and gear assemblies:
 the hollow shaft defines two first apertures and two second apertures;   the at least one first cam follower is two first cam followers; and   the at least one second cam follower is two second cam followers.   
     
     
         4 . The transmission of  claim 3 , wherein, for each of the first and second shifting and gear assemblies:
 the first apertures are positioned at 180 degrees from each other about the central axis of the hollow shaft; and   the second apertures are positions at 180 degrees from each other about the central axis.   
     
     
         5 . The transmission of  claim 4 , wherein, for each of the first and second shifting and gear assemblies, the first apertures are positioned at 90 degrees from the second apertures about the central axis. 
     
     
         6 . The transmission of  claim 1 , wherein each of the first and second shifting and gear assemblies further comprises:
 a spindle operatively connected to the shift actuator and the cam; and   wherein the shift actuator selectively rotates the spindle, and in response to the rotation of the spindle the cam translates in the hollow shaft.   
     
     
         7 . The transmission of  claim 1 , wherein, for each of the first and second shifting and gear assemblies, the cam defines:
 at least one first ramp and at least one second ramp on opposite sides thereof, the at least one first ramp and the at least one second ramp being circumferentially aligned with the at least one first cam follower; and   at least one third ramp and at least one fourth ramp on opposite sides thereof, the at least one third ramp and the at least one fourth ramp being circumferentially aligned with the at least one second cam follower.   
     
     
         8 . The transmission of  claim 1 , wherein, for each of the first and second shifting and gear assemblies:
 the at least one first cam follower is at least one first shift pawl; and   the at least one second cam follower is at least one second shift pawl.   
     
     
         9 . The transmission of  claim 1 , wherein, for each of the first and second shifting and gear assemblies:
 the cam has a cam width; and   the distance measured in the direction parallel to the central axis of the hollow shaft between the at least one first cam follower and the at least one second cam follower is less than or equal to 0.4 times the cam width.   
     
     
         10 . The transmission of  claim 1 , wherein each of the first and second shifting and gear assemblies further comprises:
 a seventh gear rotationally mounted on the hollow shaft, the hollow shaft defining at least one third aperture in axial alignment with the seventh gear, the second gear being disposed between the first and seventh gears; and   at least one third cam follower disposed in the at least one third aperture;   the distance between the at least one first cam follower and the at least one second cam follower being a first distance;   a distance measured in the direction parallel to the central axis of the hollow shaft between the at least one second cam follower and the at least one third cam follower being less than or equal to 1.1 times the width of the minimum cam contact surface;   in response to the cam being axially aligned with the at least one third cam follower, the cam displacing the at least one third cam follower radially outward to engage the seventh gear to rotationally fix the seventh gear to the hollow shaft.   
     
     
         11 . The transmission of  claim 10 , wherein, for each of the first and second shifting and gear assemblies:
 the at least one first aperture is circumferentially aligned with the at least one third aperture; and   the at least one second aperture is positioned at 90 degrees from the at least one third aperture about the central axis of the hollow shaft.   
     
     
         12 . An electric bicycle comprising:
 a frame;   a handlebar operatively connected to the frame;   a front wheel operatively connected to the handlebar;   a rear wheel operatively connected to the frame;   a transmission connected to the frame, the transmission comprising:
 an input shaft; 
 a shifting and gear assembly comprising:
 a hollow shaft parallel to the input shaft; 
 a first gear rotationally mounted on the hollow shaft, the hollow shaft defining at least one first aperture in axial alignment with the first gear; 
 at least one first cam follower disposed in alignment with the at least one first aperture; 
 a second gear rotationally mounted on the hollow shaft, the hollow shaft defining at least one second aperture in axial alignment with the second gear; 
 at least one second cam follower disposed in alignment with the at least one second aperture; 
 a cam disposed in the hollow shaft, the cam having a minimum cam contact surface, the minimum cam contact surface having a width measured in a direction parallel to a central axis of the hollow shaft, a distance measured in the direction parallel to the central axis of the hollow shaft between the at least one first cam follower and the at least one second cam follower being less than or equal to 1.1 times the width of the minimum cam contact surface; and 
 a shift actuator operatively connected to the cam, the shift actuator selectively translating the cam in the hollow shaft along the central axis of the hollow shaft, 
 in response to the cam being axially aligned with the at least one first cam follower, the cam displacing the at least one first cam follower radially outward to engage the first gear to rotationally fix the first gear to the hollow shaft, 
 in response to the cam being axially aligned with the at least one second cam follower, the cam displacing the at least one second cam follower radially outward to engage the second gear to rotationally fix the second gear to the hollow shaft; 
 
 a third gear mounted to the input shaft, the third gear being rotationally fixed relative to the input shaft, the first gear engaging the third gear; and 
 a fourth gear mounted to the input shaft, the fourth gear being rotationally fixed relative to the input shaft, the second gear engaging the fourth gear; 
   a crankshaft operatively connected to the input shaft to drive the transmission;   an electric motor operatively connected to the input shaft to drive the transmission;   a drive sprocket operatively connected to and driven by the hollow shaft;   a driven sprocket connected to the rear wheel to drive the rear wheel;   a flexible drive member engaging the drive and driven sprockets;   a pair of crank arms connected to the crankshaft; and   a battery pack connected to the frame and electrically connected to the electric motor.